|Abstracts on Global Climate Change|
Day-to-day variation in sea-surface temperature reduces sooty tern Sterna fuscata foraging success on the Great Barrier Reef, Australia
Erwin, CA Congdon, BC
MARINE ECOLOGY-PROGRESS SERIES 331: 255-266
Many seabird species threatened by global climate change are found mainly or exclusively in tropical regions. A shortage of long-term data linking climatic variation, oceanography and tropical seabird reproductive biology at both within- and between-season temporal scales means that the potential impact of climate change on these species is largely unknown. The sooty tern Sterna fuscata, an almost ubiquitous tropical seabird, has been declining on the Great Barrier Reef (GBR), Australia, over the last 3 decades. We examined the relationship between sooty tern foraging success and sea-surface temperature (SST) at Michaelmas Cay over 2 consecutive breeding seasons. Consistent patterns were observed with significant negative relationships between day-to-day variation in SST and both the amount of food fed to chicks and the feeding frequency during the latter two-thirds of each breeding season. At the beginning of each breeding cycle, rapid changes in foraging success highlighted that other within-season mechanisms also influence sooty tern reproductive potential. Our results suggest a previously undescribed spatial and temporal link between SST and sooty tern reproduction. Combined with previous findings for the southern GBR, this suggests that SST variation can influence the foraging success of multiple tropical seabird species at a reef-wide scale and implies a significant negative effect of forecasted climatic changes on seabirds breeding on the GBR.
Namaqualand’s climate: Recent historical changes and future scenarios
MacKellar, NC Hewitson, BC Tadross, MA
JOURNAL OF ARID ENVIRONMENTS 70:4 604-614
A brief outline of some issues concerning global climate change research is presented before discussing local-scale changes in Namaqaland’s rainfall. Using a gridded data set derived through interpolation of station records, trends in observed rainfall for the period 1950-1999 are discussed. To assess what changes may occur during the 21st century, the downscaled results of six different General Circulation Model projections are presented. The historical trends show some clear spatial patterns, which depict regions of wetting in the central coastal belt and the north-eastern part of the domain, and extensive drying along the escarpment. Reasonably good agreement is shown by the different downscaled projections. These suggest increased late summer convective precipitation in the north-east, but extensive drying along the coast in early and mid winter consistent with the poleward retreat of rain-bearing mid-latitude cyclones. (c) 2006 Elsevier Ltd. All rights reserved.
Namaqualand - A brief overview of the physical and floristic environment
JOURNAL OF ARID ENVIRONMENTS 70:4 570-587
This paper provides a brief introduction to the physical environment of Namaqualand as well as an overview of patterns of plant diversity. The diverse array of parent material and geological processes that have shaped the region since the break up of Gondwanaland have created a complex, and sometimes dynamic physical environment, that is partly responsible for the patterns and processes observed in the biota today. The contemporary climate is characterised by relatively reliable, albeit low (50-250 mm pa), winter rainfall (> 60% winter precipitation) arriving between May and September. East of the central mountains, tropical thunderstorms penetrate the region in late summer (February April). The presence of the cold Atlantic Ocean in the west not only moderates temperatures throughout Namaqualand (mean max summer temperature < 30 degrees C), but also provides alternative sources of moisture in the form of coastal fog and heavy dew experienced in winter months. Recent analyses show that the flora of the Succulent Karoo is part of the Cape Floral Kingdom, now termed the Greater Cape Floral Kingdom. It is one of only two desert regions recognised as a global biodiversity hot-spot and contains an estimated 6356 plant species in 168 families and 1002 genera. Namaqualand, which comprises about one quarter of the area of the Succulent Karoo, contains about 3500 species in 135 families and 724 genera, with about 25% of this flora endemic to Namaqualand. This remarkable diversity, however, is not distributed evenly throughout the region, but is concentrated in many local centres of endemism usually associated either with quartzite mountain complexes or lag-gravel plains (quartz-patches). A major exception to the general pattern of centres of diversity is the true Fynbos vegetation of the highest Kamiesberg peaks where rainfall exceeds 400 mm pa. Suggested determinants of the region’s exceptional floral diversity include the complex physical environment, a unique past and present climate and the region’s diverse fauna, most notably insects. The challenge for the current inhabitants and scientists working in the region is to develop a better understanding of this ecosystem so that they will be equipped to deal with the challenges posed by the demands for land and the prospect of global climate change. (c) 2007 Elsevier Ltd. All rights reserved.
Sifting the future from the past: a personal assessment of trends impacting the Australian rangelands
RANGELAND JOURNAL 29:1 3-11
The fore-sighting exercise undertaken at the Australian Rangeland Society Conference at Port Augusta 10 years ago in 1996 developed four scenarios: ‘economic growth’, ‘best practice’, ‘extra green’ and ‘partial retreat’. These were later collapsed into two broad directions, ` looking out’ (the economic rewards generated by a full application of free market policies with rangeland enterprises having strong external linkages will result in production and management efficiencies which benefit the Australian economy) and ‘looking in’ (rangeland Australia and its human, economic and ecological resources will be best served by the development and maintenance of strong local communities in each rangeland region). It was anticipated that ` looking out’ would apply to only a few rangeland regions where pastoral production is highly valued and rangelands are resilient; ` looking in’ would apply to the majority of the rangelands where other values might outweigh pastoral production in the future and where the rangeland resource is considered less resilient. Given the world’s embrace of economic and trade globalisation, and the dominance in the federal sphere of one coalition government and one prime minister, it seems inevitable that across Australia the last 10 years were dominated by the ` looking out’ direction, while many marginal rangelands had few options but to ‘look in’. The 1996 discussions failed to appreciate fully the importance in shaping today’s world of singular issues such as terrorism, global climate change, potential disease pandemics, the emergence of China and India and, in an Australian rangelands context, the continuing success of the northern beef industry. In the interim, rangelands science has produced an impressive underpinning of integrative information led both by industry investment and government funding. However, long-term resilience is still not assured in many areas of Australia’s rangelands. It continues to be outpaced by those four horsemen of the ( rangelands) apocalypse: the need for growth, periodic droughts, personal gain and introduced organisms. During the next 2 decades the rangelands will be buffeted by many of the same old issues and well as obvious emerging ones. Important human-centric ones will be the tension between European and Aboriginal demographic trends, the increased economic dominance of mining, tourism and defence in the rangelands, and the ‘sponge effect’ of successful towns and particular enterprises. Ecological and bio-physical issues will include carbon trading, energy generation, water catchments, weeds and diseases and agricultural incursions into the northern rangelands. The broad directions of ‘looking out’ and ‘looking in’ still retain some currency for today’s rangeland decision makers but are now embedded in far stronger and shifting currents that are frequently determined by global and national dynamics, rather than local issues. A distinguishing feature of the Australian rangelands is that they are still essentially intact (apart from their fauna) in a world context and may gain future ecological and economic advantage by remaining so. How to retain this status remains one of the great challenges for the next generation of Australian rangelanders.
Coastal flood risk analysis using landsat-7 ETM+ imagery and SRTM DEM: A case study of Izmir, turkey
Demirkesen, AC Evrendilek, F Berberoglu, S Kilic, S
ENVIRONMENTAL MONITORING AND ASSESSMENT 131:1-3 293-300
The Intergovernmental Panel on Climate Change (IPCC) reports an acceleration of the global mean sea-level rise (MSLR) in the twentieth century in response to global climate change. If this acceleration remains constant, then some coastal areas are most likely to be inundated by the year 2100. The ability to identify the differential vulnerability of coastlines to future inundation hazards as result of global climate change is necessary for timely actions to be taken. Yildiz et al. (Journal of Mapping, 17, 1 75, 2003) reported that the local MSLR in the city of Izmir rose at a rate of 6.8 +/- 0.9 mm year(-1) between 1984 and 2002. In this study, the spatial distribution of the coastal inundation hazards of Izmir region was determined using not only land-use and land-cover (LULC) types derived from the maximum likelihood classification of Landsat-7 Enhanced Thematic Mapper Plus (ETM+) multi-spectral image set but also the classification of the digital elevation model (DEM) acquired by the shuttle radar topography mission (SRTM). Coastal areas with elevations of 2 and 5 m above mean sea-level vulnerable to inundation were found to cover 2.1 and 3.7% of the study region (6,107 km(2)), respectively. Our findings revealed that Menemen plain along Gediz river, and the settlements of Karsiyaka, Alacati, Aliaga, Candarli and Selcuk are at high risk in order of decreasing vulnerability to permanent and episodic inundation by 2100 under the high MSLR scenarios of 20 to 50 mm year(-1).
Experimental studies on homogeneous charge CI engine fueled with LPG using DEE as an ignition enhancer
Jothi, NKM Nagarajan, G Renganarayanan, S
RENEWABLE ENERGY 32:9 1581-1593
Producing and using renewable fuels for transportation is one approach for sustainable energy future for the world. A renewable fuel contributes lesser global climate change. The present work reports on the utilization of liquified petroleum gas (LPG) as a primary fuel with diethyl ether (DEE) as an ignition enhancer in a direct injection diesel engine. LPG has a simpler hydrocarbon structure than conventional fuels. DEE is recently reported as a renewable fuel and to be a low-emission high-quality diesel fuel replacement. A single cylinder, four-stroke, water-cooled naturally aspirated DI diesel engine having rated output of 3.7 kW at 1500 rpm was used for the experiments. Measurements were made to study the performance, combustion and emissions characteristics. From the results, it is observed that, the brake thermal efficiency lower by about 23% at full load with a reduction of about 65% NO emission than the diesel operation. The maximum reduction in smoke and particulate emissions is observed to be about 85% and 89%, respectively, when compared to that of diesel operation, however an increase in CO and HC emissions was observed. (c) 2006 Elsevier Ltd. All rights reserved.
Periodic solutions for soil carbon dynamics equilibriums with time-varying forcing variables
Martin, MP Cordier, S Balesdent, J Arrouays, D
ECOLOGICAL MODELLING 204:3-4 523-530
Numerical models that simulate the dynamics of carbon in soil are increasingly used to improve our knowledge and help our management of the carbon cycle. Calculation of the long-term behavior of these models is necessary in many applications but encounters the difficulty of managing the periodic forcing variables, e.g. seasonal variations, such as carbon inputs and decomposition rates. This calculation is conventionally done by running the model over large time durations or by assuming constant forcing variables. Two methods, which make it possible to rapidly compute periodic solutions taking into account the time variations of these variables, are proposed. The first one works on discrete-time models and the second one on continuous-time models involving Fourier transforms. Both methods were tested on the Rothamsted carbon model (RothC), a discrete-time model which has also been given a continuous approximation, using realistic and unrealistic sets of time-varying forcing functions. Both methods provided an efficient way to compute the periodic solutions of the RothC model within the application domain of the model. Compared to running the discrete model to the equilibrium, reduction in the computational cost was of up to 95% at the expense of a maximum absolute error of 1% for the estimation of carbon stocks. For specific distributions of the forcing variables the use of Fourier transform of zero order, which was equivalent to assume constant forcing variables, led to a maximum absolute error of SS% in the estimation of the long-term behavior of the model. There, a Fourier transform of order higher than zero is required. (C) 2007 Elsevier B.V. All rights reserved.
Simulation of seasonal precipitation and raindays over Greece: a statistical downscaling technique based on artificial neural networks (ANNs)
Tolika, K Maheras, P Vafiadis, M Flocasc, HA Arseni-Papadimitriou, A
INTERNATIONAL JOURNAL OF CLIMATOLOGY 27:7 861-881
A statistical downscaling technique based on artificial neural network (ANN) was employed for the estimation of local changes on seasonal (winter, spring) precipitation and raindays for selected stations over Greece. Empirical transfer functions were derived between large-scale predictors from the NCEP/NCAR reanalysis and local rainfall parameters. Two sets of predictors were used: (1) the circulation-based 500 hPa and (2) its combination along with surface specific humidity and raw precipitation data (nonconventional predictor). The simulated time series were evaluated against observational data and the downscaling model was found efficient in generating winter and spring precipitation and raindays. The temporal evolution of the estimated variables was well captured, for both seasons. Generally, the use of the nonconventional predictors are attributed to the improvement of the simulated results. Subsequently, the present day and future changes on precipitation conditions were examined using large-scale data from the atmospheric general circulation model HadAM3P to the statistical model. The downscaled climate change signal for both precipitation and raindays, partly for winter and especially for spring, is similar to the signal from the HadAM3P direct output: a decrease of the parameters is predicted over the study area. However, the amplitude of the changes was different. Copyright (c) 2006 Royal Meteorological Society
Simulated changes in active/break spells during the Indian summer monsoon due to enhanced CO2 concentrations: assessment from selected coupled atmosphere-ocean global climate models
Mandke, SK Sahai, AK Shinde, MA Joseph, S Chattopadhyay, R
INTERNATIONAL JOURNAL OF CLIMATOLOGY 27:7 837-859
The simulations by ten coupled GCMs under the Intergovernmental Panel on Climate Change Assessment Report-4 are used to study the implication of possible global climate change on active/break spells of the Indian summer monsoon (ISM). The validation of the mean daily cycle of the summer monsoon precipitation over the Indian core region and the spatial pattern of the ISM precipitation climatology with observation suggest that six models simulate fairly well, whereas four models differ from observation. Thus, the identification of activelbreak spells is confined to six models. The sensitivity to climate change has been assessed from two experiments, namely, 1% per year CO2 increase to doubling and 1% per year CO2 increase to quadrupling. The changes in the daily mean cycle and the standard deviation of precipitation, frequency, and duration of active/break spells in future climate change are uncertain among the models and at times among two experiments. The break composite precipitation anomalies strengthen and spread moderately (significantly) in the doubled (quadrupled) CO2 experiment. Copyright (c) 2006 Royal Meteorological Society.
Storage and release of fossil organic carbon related to weathering of sedimentary rocks
Copard, Y Amiotte-Suchet, P Di-Giovanni, C
EARTH AND PLANETARY SCIENCE LETTERS 258:1-2 345-357
The biogeochemical carbon cycle, which plays an undeniable role in global climate change, is defined both by the size of carbon reservoirs (such as the atmosphere, biomass, soil and bedrock) and the exchange between them of various mineral and organic carbon forms. Among these carbon forms, fossil organic carbon (FOC) (i.e., the ancient organic matter stored in sedimentary rocks) is widely observed in modem environments but is not included in the supergene carbon budget. Using a digitized map of the world and an existing model of CO2 consumption associated with rock weathering, we establish the global distribution of FOC stored in the first meter of sedimentary rocks and a first estimation of annual FOC delivery to the modem environment resulting from chemical weathering of these rocks. Results are given for the world’s 40 major river basins and extended to the entire continental surface. With a mean value of I 100 10(9) t, mainly controlled by shale distribution, the global FOC stock is significant and comparable to that of soil organic carbon (1500 10(9) t). The annual chemical delivery of FOC, estimated at 43 10(6) t yr(-1) and controlled by the areal distribution of shales and runoff is of the same order of magnitude as the FOC output flux to oceans. Chemical weathering of bedrock within the Amazon basin produces one-quarter of the total global flux of FOC derived from chemical weathering, and thus is expected to govern FOC release on a global scale. These results raise important questions concerning the role of FOC in the modem carbon cycle as well as the origin and the budget of carbon in soils and rivers. (C) 2007 Elsevier B.V. All rights reserved.
Strontium isotope tracing of terrigenous sediment dispersal in the Antarctic Circumpolar Current: Implications for constraining frontal positions
Hemming, SR van de Flierdt, T Goldstein, SL Franzese, AM Roy, M Gastineau, G Landrot, G
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 8: -
 The vigor of the glacial Antarctic Circumpolar Current (ACC) and the locations of frontal boundaries are important parameters for understanding the role of the Southern Ocean in global climate change. Toward the goal of understanding the locations of currents we present a survey of Sr isotope ratios in terrigenous sediments around the perimeter of Antarctica. The pattern of the variations within the modern ACC is used to suggest that terrigenous sediment from Antarctica is injected into the ACC via the Ross and Weddell gyres in the south. North of the main ACC the Sr isotopes reflect continental contributions from Africa, Australia-New Zealand, and South America. Along a transect northward from the Ross Sea, Sr isotope ratios show a decrease from higher values in the south ( Antarctic provenance) to lower values in the north ( provenance from New Zealand). This otherwise monotonic decrease is interrupted within the ACC by a “zigzag” to lower and then higher values, which accompanies minimum terrigenous flux. This zigzag requires contributions from two additional sediment sources beyond the main Antarctic and New Zealand end-members. The lower Sr isotope ratios are attributable to greater contributions from basaltic sources within the current, a consistent pattern around the ACC. The samples with higher Sr isotope ratios point to an additional contributor, possibly a wind-transported component from Australia. During the LGM there is a systematic geographical variation in the Sr isotope ratios, similar to that of the Holocene. A small offset of the zigzag to the north ( approximately 1 degrees-2 degrees) may indicate a small northward shift of the southern boundary of the ACC. More highly resolved data are required to test whether this northward shift is really significant and whether it applies to other ACC fronts during the LGM.
Dominant factors controlling glacial and interglacial variations in the treeline elevation in tropical Africa
Wu, HB Guiot, J Brewer, S Guo, ZT Peng, CH
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 104:23 9720-9724
The knowledge of tropical palaeoclimates is crucial for understanding global climate change, because it is a test bench for general circulation models that are ultimately used to predict future global warming. A longstanding issue concerning the last glacial maximum in the tropics is the discrepancy between the decrease in sea-surface temperatures reconstructed from marine proxies and the high-elevation decrease in land temperatures estimated from indicators of treeline elevation. In this study, an improved inverse vegetation modeling approach is used to quantitatively reconstruct palaeoclimate and to estimate the effects of different factors (temperature, precipitation, and atmospheric CO2 concentration) on changes in treeline elevation based on a set of pollen data covering an altitudinal range from 100 to 3,140 m above sea level in Africa. We show that lowering of the African treeline during the last glacial maximum was primarily triggered by regional drying, especially at upper elevations, and was amplified by decreases in atmospheric CO2 concentration and perhaps temperature. This contrasts with scenarios for the Holocene and future climates, in which the increase in treeline elevation will be dominated by temperature. Our results suggest that previous temperature changes inferred from tropical treeline shifts may have been overestimated for low-CO2 glacial periods, because the limiting factors that control changes in treeline elevation differ between glacial and interglacial periods.
Evidence for carbon sequestration by agricultural liming
Hamilton, SK Kurzman, AL Arango, C Jin, LX Robertson, GP
GLOBAL BIOGEOCHEMICAL CYCLES 21:2 -
 Agricultural lime can be a source or a sink for CO2, depending on whether reaction occurs with strong acids or carbonic acid. Here we examine the impact of liming on global warming potential by comparing the sum of Ca2+ and Mg2+ to carbonate alkalinity in soil solutions beneath unmanaged vegetation versus limed row crops, and of streams and rivers in agricultural versus forested watersheds, mainly in southern Michigan. Soil solutions sampled by tension indicated that lime can act as either a source or a sink for CO2. However, infiltrating waters tended to indicate net CO2 uptake, as did tile drainage waters and streams draining agricultural watersheds. As nitrate concentrations increased in infiltrating waters, lime switched from a net CO2 sink to a source, implying nitrification as a major acidifying process. Dissolution of lime may sequester CO2 equal to roughly 25 - 50% of its C content, in contrast to the prevailing assumption that all of the carbon in lime becomes CO2. The similar to 30 Tg/yr of agricultural lime applied in the United States could thus sequester up to 1.9 TgC/ yr, about 15% of the annual change in the U. S. CO2 emissions (12 Tg C/yr for 2002 - 2003). The implications of liming for atmospheric CO2 stabilization should be considered in strategies to mitigate global climate change.
Thermal stress and coral cover as drivers of coral disease outbreaks
Bruno, JF Selig, ER Casey, KS Page, CA Willis, BL Harvell, CD Sweatman, H Melendy, AM
PLOS BIOLOGY 5:6 1220-1227
Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia’s Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef- building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (> 50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.
Modelling energy systems for developing countries
Urban, F Benders, RMJ Moll, HC
ENERGY POLICY 35:6 3473-3482
Developing countries’ energy use is rapidly increasing, which affects global climate change and global and regional energy settings. Energy models are helpful for exploring the future of developing and industrialised countries. However, energy systems of developing countries differ from those of industrialised countries, which has consequences for energy modelling. New requirements need to be met by present-day energy models to adequately explore the future of developing countries’ energy systems. This paper aims to assess if the main characteristics of developing countries are adequately incorporated in present-day energy models. We first discuss these main characteristics, focusing particularly on developing Asia, and then present a model comparison of 12 selected energy models to test their suitability for developing countries. We conclude that many models are biased towards industrialised countries, neglecting main characteristics of developing countries, e.g. the informal economy, supply shortages, poor performance of the power sector, structural economic change, electrification, traditional bio-fuels, urban-rural divide. To more adequately address the energy systems of developing countries, energy models have to be adjusted and new models have to be built. We therefore indicate how to improve energy models for increasing their suitability for developing countries and give advice on modelling techniques and data requirements. (c) 2007 Elsevier Ltd. All rights reserved.
Diversity and zonal distribution of arbuscular mycorrhizal fungi on the northern slopes of the Tianshan Mountains
Shi, ZY Chen, ZC Zhang, LY Feng, G Christie, P Tian, CY Li, XL
SCIENCE IN CHINA SERIES D-EARTH SCIENCES 50: Suppl. 1 135-141
The arbuscular mycorrhizal (AM) fungal status of the 20 most common plant species distributed in 4 vegetation types (meadow steppe, desert steppe, steppe desert and typical desert) on the northern slopes of the Tianshan Mountains was investigated. Samples of the plant species and their rhizosphere soils were collected from the 4 vegetation zones and examined to compare their mycorrhizal status, AM fungal spore densities, biovolumes, and community structures. 28 AM fungal species were isolated from the rhizosphere soils: of these, 5 belonged to Acaulospora, 1 to Archaeospora and 22 to Glomus. 5 AM fungi, Glomus aggregatum, G. claroideum, G. deserticola, G. etunicatum and G. sinuosum, were observed in all 4 zonal types. No significant differences were observed in mean proportion of root length colonized by AM fungi among the plant species within each zonal type. Comparing the 4 zonal types, Plantago minuta (84.5%) in steppe desert and Eremopyrum orientale (83.1%) in typical desert showed the highest root colonizatsion rates. AM fungal spore densities and biovolumes were significantly different in the different zonal types. AM fungal spore densities and biovolumes, species richness and diversity were highest in meadow steppe and lowest in typical desert.
The efficiency gap behind the Annex I parties under the Kyoto Protocol
INTERNATIONAL JOURNAL OF SUSTAINABLE DEVELOPMENT AND WORLD ECOLOGY 14:3 225-234
With the ratification of the Kyoto Protocol, an era of global efforts to combat climate change is beginning. Countries belonging to Annex I Parties are obligated to meet their target in reducing greenhouse gas (GHG) emissions. This paper broadens the scope of research to compare the performance between two groups, Annex 11 Parties and economies in transition (EIT) Parties (both of which are in the set of Annex I Parties), undertaking responsibilities for GHG emission reduction. This differs from the traditional application of evaluation and aims to identify inherent efficiency differences across systems, rather than separately from the potential inefficiency of individual countries. An efficiency gap was found between the group of Annex 11 Parties and the group of EIT Parties, by adjusting efficiency levels. Considering a reference set, efficient Annex 11 countries are referenced, both within their own group and within the EIT group; efficient EIT countries are only benchmarked within the group. The evidence provided can shed light on the function of joint implementation, that Annex I countries will cooperate to reduce GHG emissions, based on their common, but differentiated, responsibilities and capacity for global climate change.
Eustasy and sea water Sr composition: application to high-resolution Sr-isotope stratigraphy of Miocene shallow-water carbonates
Kroeger, KF Reuter, M Forst, MH Breisig, S Hartmann, G Brachert, TC
SEDIMENTOLOGY 54:3 565-585
Oceanic Sr-87/Sr-86-isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea-level change. The present study combines analysis of sequence stratigraphy and basin architecture with Sr-isotope stratigraphy in Miocene shallow-water sediments in southern Portugal and Crete (Greece). The common method is to use smoothed global sea water Sr-isotope reference curves but here a different approach is chosen. Instead, measured Sr-isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr. Transgressive intervals are characterized by increasing Sr-isotope ratios interpreted as corresponding to intensified silicate weathering as a consequence of deglaciation, while lowstand deposits have low Sr-isotope ratios. Comparison of Sr-isotope curves and sedimentary sequences in the studied basins with independent global delta O-18 data and data on global sea-level might suggest a general relationship, supporting a connection to global climate change. Because of these relationships, the method presented herein has a high potential for use in high-resolution age dating and is also applicable in shallow-water sediments.
Expert judgements on the response of the Atlantic meridional overturning circulation to climate change
Zickfeld, K Levermann, A Morgan, MG Kuhlbrodt, T Rahmstorf, S Keith, DW
CLIMATIC CHANGE 82:3-4 235-265
We present results from detailed interviews with 12 leading climate scientists about the possible effects of global climate change on the Atlantic Meridional Overturning Circulation (AMOC). The elicitation sought to examine the range of opinions within the climatic research community about the physical processes that determine the current strength of the AMOC, its future evolution in a changing climate and the consequences of potential AMOC changes. Experts assign different relative importance to physical processes which determine the present-day strength of the AMOC as well as to forcing factors which determine its future evolution under climate change. Many processes and factors deemed important are assessed as poorly known and insufficiently represented in state-of-the-art climate models. All experts anticipate a weakening of the AMOC under scenarios of increase of greenhouse gas concentrations. Two experts expect a permanent collapse of the AMOC as the most likely response under a 4xCO(2) scenario. Assuming a global mean temperature increase in the year 2100 of 4 K, eight experts assess the probability of triggering an AMOC collapse as significantly different from zero, three of them as larger than 40%. Elicited consequences of AMOC reduction include strong changes in temperature, precipitation distribution and sea level in the North Atlantic area. It is expected that an appropriately designed research program, with emphasis on long-term observations and coupled climate modeling, would contribute to substantially reduce uncertainty about the future evolution of the AMOC.
Constructing regional scenarios for sustainable agriculture in European Russia and Ukraine for 2000 to 2070
Romanenko, IA Romanenkov, VA Smith, P Smith, JU Sirotenko, OD Lisovoi, NV Shevtsova, LK Rukhovich, DI Koroleva, PV
REGIONAL ENVIRONMENTAL CHANGE 7:2 63-77
This study estimates the consequences of climate change on cropland with and without implementation of adaptation measures, paying special attention to the maintenance of soil organic carbon (C) stocks. We examine the possibility for regional sustainable agricultural management practice that combines both maintenance and gain in soil carbon level with profit maximization. Future scenarios of Regional Agricultural Production Systems (RAPS) were constructed for 2000-2070 based on linking the effects of global climate change, predicted change in productivity parameters for the main agricultural crops, land-use and soil database parameters. The RAPS were used to examine profitability and feasibility of alternative agricultural scenarios, based on an economic model. A number of recommendations for decision making were proposed based on an assessment of the efficiency of adaptation in animal husbandry and in the crop production sector, after analysis of current percentage of perennial grass in rotation in comparison with future economic scenarios.